Intravascular catheters such as angiographic catheters are introduced from the exterior of a patient into an artery or vein. After such introduction, the catheter is advanced or maneuvered through the arteriovenous system to a desired site, which may be an area of arteriostenosis, or an area from which x-ray contrast media is injected into the system, or the interior of the heart itself, for example. As described for example in the Stevens U.S. Pat. No. 4,000,739, such catheter may be emplaced by first inserting a hollow needle with a trocar through the skin into the lumen of the desired blood vessel. Following this, a guidewire is passed through the needle and advanced up the artery or vein toward the area or the organ to be studied. The needle can then be removed, leaving the guidewire in the vessel. Following this, a catheter introducer comprising a tubular sheath and a removable hollow stylet or dialator unit may be advanced together over the wire into the vessel. Then, the guidewire and the dilator unit are removed, leaving only the catheter introducer sheath present in the vessel.
Then, the desired catheter can be advanced through the sheath into the vessel.
A catheter introducer sheath carries a hub having hemostasis valve means on its proximal end to avoid uncontrolled bleeding and air embolism. The dilator unit, and then the catheter, pass through the hemostasis valve, which is typically a latex partition having a slit of well known design. Various designs of hemostasis valves and catheter introducers are in commercial use.
Problems with the prior art catheter introducers which have arisen include problems where the catheter sliding through the bore of the catheter introducer, and the catheter introducer itself in the artery or vein, exhibit undesirably high frictional characteristics. Catheters are advanced through emplaced catheter introducers a very substantial distance into the body to reach the heart or coronary arteries. Thus, it is distinctly undesirable for frictional problems between the catheter and catheter introducer to arise.
Another problem of prior art catheter introducers is that, of course, they must be of a minimum outer diameter to minimize the size of the incision in an artery. This requires the catheter introducer to be of as thin a wall as possible. However, thin-walled catheter introducers display a significant propensity for kinking. Also, it is desireable in many circumstances for the catheter introducer to be relatively stiff and will high hoop strength although flexible, and to have a distal tip which is materially softer and more flexible than the body of the catheter introducer.
In accordance with this invention, a reinforced catheter introducer is provided to exhibit substantial kink resistance coupled with the desired, resilient stiffness of the main body of the catheter introducer, and further coupled with a tapered, softer distal tip. The catheter introducer of this invention can also be of very low friction to solve frictional resistance problems which have been previously encountered in prior art catheter introducers.